Epoxy Paint Interaction

[Roger Long]

Before repainting some woodwork on my boat, I sealed an area where a puddle of water tends to sit and soak into the wood with System Three epoxy. After it was hard, I put the first coat of oil based enamel paint on the hatch cover. Three days later, the paint is dry and hard everywhere except over the epoxy where it is still tacky.

Any ideas? Will this resolve itself?

Epoxy was hard and sanded lightly before painting.

 

[Podjo]

My guess is that it will not dry. We had the same issue where on some teak that was coated with epoxy and then coated with varnish. After three days the varnish was not dry. My wife called System Three and they gave her a list of compatible varnishes that would work with their products. I remember that System Threes customer support was very helpful. My feeling is that each product, regardless of brand, has similar compatibility issues.

 

[RECESS]

nevermind, not great advice

 

[sandpiper10471]

I wonder if the amine blush that can develop on epoxy surfaces is interacting with your paint. I know for sure that gelcoat doesn't always cure over epoxy and is particularly problematic, in my experience, with System Three. Sometimes a barrier coat of vinylester solves the problem. I suggest scraping off the uncured paint, cleaning, washing and sanding the epoxy patch and trying again. If that doesn't work, try a barrier coat, possibly West epoxy.

 

[gettinthere]

an epoxy with amines? Why bother!!!

Surf here: http://www.epoxyusa.com/category_s/3.htm (part of Epoxy Products)

Good stuff. And good support. And great prices.

A basic no blush epoxy 2 part kit to make 1.5 Gallons is $87.

 

[Roger Long]

There is definitely something funky about System Three. I just scraped the mess off and it looks like most of the epoxy came up with the paint that was barely tacky. Paint in the same coat but over either bare wood or the old paint was hard as a rock.

I remember now that a different paint that I put over some epoxy repairs in the bilge did the same thing. It eventually hardened but was tacky for weeks. I thought it was just because the fiberglass hull was cold in the middle of winter. I'm quite sure the System Three bottles I just used were left over from that project.

Question now is whether new paint will dry over the scrapped portion. I'll let you know.

A bit later:

Good response on the Wooden Boat Forum:

http://forum.woodenboat.com/showthr...t-compatibility-problem&p=2918984#post2918984

It also appears that there are epoxies available that do not have the amine solvents that leech out and turn the paint to mush for days after application.

http://www.epoxyproducts.com/marine.html

 

[Prime Time]

Primer Over Epoxy

I don't think system 3 has an amine blush issue, but check with company.

Many paints won't cover epoxy, and you need a primer. I remember having to use a primer over my West System Epoxy bottom job before using an ablative bottom paint.

 

[Roger Long]

Next morning:

Scraped it right down last night, scrubbed with Acetone, sanded, scrubbed again. Could hardly see any epoxy left. Put on some test patches of paint and they were barely tacky this morning. Going to try the Cobalt Blue.

I'm sure glad I learned this on some very small areas.

 

[Barnacle Bill]

You can only put the epoxy over a dry surface. If there was any moisture in the substrate you were applying the epoxy to, then you will have some issues with curing there. Also, there usually is an amine blush that must be washed before putting anything over epoxy resin that has cured, including another coat of epoxy. Lastly, not all varnishes are compatible with epoxies. I have found Captain's Varnish is best when used over epoxies for those who builld cedar strip canoes, for example.

 

[Roger Long]

Well, for the data point and learning experience this project can provide, here is what I am doing after scraping off the soft paint.

I scrubbed with Acetone and sanded last night and put some small test patches on. This morning, they were like the paint had just been applied. Not even tacky.

I asked for Cobalt Blue at the art supply store and they told me it was a paint. Maybe it works because of the Cobalt but they seemed familiar with the issues and sold me a bottle of cobalt dryer, which turns out to be the Japan Dryer I've heard of before. I've applied paint with it mixed in as a thin coat and we'll see what happens.

This is a small and out of the way area so it's a good place to experiment. I'll let you now how it turns out.

Thanks to everyone for all the great information.